Probucol is a well-known antioxidant that is related to antioxidant compounds such as 2-(3)-tertiary butyl-4-hydroxyanisole, 2,6-di-tertiary butyl-4-methylphenol and the like. These compounds are used in food and food products to prevent oxidative deterioration.
Probucol is represented by the following structural formula

The preparation of this compound is a multistep process, typically starting by reacting a solution of the appropriately-substituted 4-mercaptophenol with acetone, in the presence of a catalytic amount of a strong acid. Probucol precipitates from the reaction mixture and is readily separated and purified. The reaction is described in detail in U.S. Pat. No. 3,862,332 (Barhhart et al).
Similarly, probucol and certain of its derivatives are also described in U.S. Pat. No. 3,485,843 (Wang), U.S. Pat. No. 3,576,833 (Neuworth) and U.S. Pat. No. 4,985,465 (Handler).
Probucol and its derivatives possess pharmaceutical properties that include antiatherogenesis, lipid lowering and the like. But probucol and numerous of its derivatives are poorly soluble in body fluids.
In order to avoid the low water solubility problems associated with probucol utilization in the body, more water-soluble derivatives have been prepared. Thus, U.S. Pat. No. 5,262,439 (Parthasarathy), incorporated herein in its entirety by reference, discloses a class of water-soluble probucol derivatives having one or more ester groups replacing the phenolic hydroxyl group of the probucol molecule. Some of the compounds disclosed in this reference have polar or charged functionalities attached to the ester group, e.g., the groups carboxylic acid, amide, amino, and aldehyde. The method disclosed for preparing these water-soluble probucol compounds involves the reaction of probucol with the carboxylic acid anhydride compound bearing the desired polar or charged functionality in the presence of a catalyst.
Similarly, U.S. Pat. Nos. 6,323,359 and 6,548,699 also disclose water soluble derivatives of probucol. The compounds set forth in the former patent are produced by a process involving the reaction of a probucol dianion with carboxylic acid anhydrides. The compounds disclosed in U.S. Pat. No. 6,548,699 are synthesized by reaction of probucol with, inter alia, halo-substituted aliphatic esters.
The prior art processes are disadvantageous, since they are not effective in producing the desired alkylated derivatives of probucol in any appreciable yields.
Accordingly, it is desirable to have available a process to efficiently prepare probucol derivatives in high yields.